Wholly aromatic polyester resins have long been known. For instance, p-hydroxybenzoic acid homopolymer and copolymers have been provided in the past and are commercially available. Those wholly aromatic polyesters normally encountered in the prior art have tended to be somewhat intractable in nature and to present substantial difficulties if one attempts to melt process the same while employing conventional melt processing procedures. Such polymers commonly are crystalline in nature, relatively high melting or possess a decomposition temperature which is below the melting point, and when molten frequently exhibit an isotropic melt phase. Molding techniques such as compression molding or sintering may be utilized with such materials; however, injection molding, melt spinning, etc. commonly have not been viable alternatives or when attempted commonly have been accomplished with difficulty. Such polymers commonly cannot be melt extruded to form nondegraded fibers. Even those wholly aromatic polymers which exhibit a melting point below their decomposition temperature commonly melt at such high temperatures that quality fibers may not be melt spun. For instance, fibers melt extruded at extremely high temperatures commonly possess a voidy internal structure and diminished tensile properties.
Representative publications which discuss wholly aromatic polyesters include: (a) Polyesters of Hydroxybenzoic Acids, by Russell Gilkey and John R. Caldwell, J. of Applied Polymer Sci., Vol. II, Pages 198 to 202 (1959), (b) Polyarylates (Polyesters From Aromatic Dicarboxylic Acids and Bisphenols), by G. Bier, Polymer, Vol. 15, Pages 527 to 535 (August 1974), (c) Aromatic Polyester Plastics, by S. G. Cottis, Modern Plastics, Pages 62 to 63 (July 1975), and (d) Poly (p-Oxybenzoyl Systems): Homopolymer for Coatings: Copolymers for Compression and Injection Molding, by Roger S. Storm and Steve G. Cottis, Coatings Plast. Preprint, Vol 34, No. 1, pages 194 to 197 (April 1974). See also, U.S. Pat. Nos. 3,039,994; 3,169,121; 3,321,437; 3,553,167; 3,637,595; 3,651,014; 3,723,388; 3,759,870; 3,767,621; 3,787,370; 3,790,528; 3,829,406; 3,890,256; and 3,975,487.
Also, it more recently has been disclosed that certain polyesters may be formed which exhibit melt anistropy. See for instance, (a) Polyester X7G-A Self Reinforced Thermoplastic, by W. J. Jackson, Jr., H. F. Kuhfuss, and T. F. Gray, Jr., 30th Anniversary Technical Conference, 1975 Reinforced Plastics/Composites Institute, The Society of the Plastics Industry, Inc., Section 17-D, Pages 1 to 4, (b) Belgian Pat. Nos. 828,935 and 828,936, (c) Dutch No. 7505551, (d) West German Pat. Nos. 2520819 and 2520820, (e) Japanese No. 43-233, (f) U.S. Pat. Nos. 3,991,013 and 3,991,014.
In commonly assigned U.S. Ser. No. 686,189, filed May 13, 1976 (now U.S. Pat. No. 4,067,852), by Gordon W. Calundann entitled "Improved Melt Processable Thermotropic Wholly Aromatic Polyester and Process for Its Production" is claimed a generic invention wherein a wholly aromatic polyester (as defined) consists essentially of recurring units of p-oxybenzoyl moiety, 2,6-dicarboxynaphthalene moiety, and symmetrical dioxy aryl moiety.
In commonly assigned U.S. Ser. No. 789,374, filed Apr. 20, 1977 (now U.S. Pat. No. 4,083,829) by Gordon W. Calundann, Herbert L. Davis, Frederick J. Gorman, and Robert M. Mininni, entitled "Improved Melt Processable Thermotropic Wholly Aromatic Polyester Which Is Particularly Suited for Fiber Formation" is specifically claimed a species of the generic invention defined in U.S. Ser. No. 686,189 wherein an isophthaloyl moiety and/or metadioxy phenyl moiety recur in the wholly aromatic polyester in addition to p-oxybenzoyl moiety, 2,6-dicarboxynaphthalene moiety, and symmetrical dioxy aryl moiety.
In commonly assigned U.S. Ser. No. 832,147 filed Sept. 12, 1977, now abandoned by Gordon W. Calundann, entitled "Melt Processable Thermotropic Wholly Aromatic Polyester" is claimed a wholly aromatic polyester (as defined) which consists essentially of recurring units of p-oxybenzoyl moiety, 2,6-dioxynaphthalene moiety, and terephthaloyl moiety.
In commonly assigned U.S. Ser. No. 832,713 filed Sept. 12, 1977 by Gordon W. Calundann, entitled "Melt Processable Thermotropic Wholly Aromatic Polyester Comprising Both Para-Oxybenzoyl and Meta-Oxybenzoyl Moieties" is claimed a wholly aromatic polyester (as defined) which consists essentially of recurring units of p-oxybenzoyl moiety, m-oxybenzoyl moiety, 2,6-dicarboxynaphthalene moiety, and symmetrical dioxy aryl moiety.
It is an object of the present invention to provide an improved melt processable wholly aromatic polyester.
It is an object of the present invention to provide an improved wholly aromatic polyester which is suited for the formation with ease of quality molded articles, melt extruded fibers, and melt extruded films.
It is an object of the present invention to provide an improved melt processable wholly aromatic polyester capable of forming a thermotropic melt phase at a temperature below approximately 350.degree. C., preferably below 325.degree. C., and most preferably below approximately 300.degree. C.
It is an object of the present invention to provide an improved wholly aromatic polyester which forms a highly tractable melt phase.
It is an object of the present invention to provide an improved wholly aromatic polyester which satisfactorily can be formed without precise regard to the stoichiometric proportions of reactants.
It is an object of the present invention to provide an improved wholly aromatic polyester which forms a thermotropic melt phase at a temperature well below its decomposition temperature and which may form quality high performance fibers.
It is an object of the present invention to provide improved wholly aromatic polyester fibers which particularly are suited for use as fibrous reinforcement in a rubber matrix.
It is another object of the present invention to provide an improved wholly aromatic polyester which readily may be melt extruded to form a film.
It is another object of the present invention to provide an improved wholly aromatic polyester which readily may be injection molded to form a molded article (which optionally may be fiber reinforced) exhibiting superior tensile strength, flex strength, and impact strength.
These and other objects, as well as the scope, nature and utilization of the invention will be apparent to those skilled in the art from the following detailed description.